1. Field of the Invention
The present invention relates to an optical transmitting module, in particular, an optical transmitting module having a CAN type package.
2. Related Prior Art
Recently, it is requested that a terminator should be installed within an optical transmitting module or an optical transmitting sub-assembly to match an input impedance thereof to the line impedance as the transmission speed in the optical communication system which increases and reaches to giga-hertz (GHz) band. Moreover, it is generally applied for an optical active device, such as a semiconductor laser diode and a pre-amplifier, to dissipate larger power in order to operate in such high speed signal.
In the optical transmitting module or the optical transmitting sub-assembly having a CAN type package, the miniaturization of the package may be easily carried out. On the other hand, to install the terminator within the CAN type package is so hard because of its small sized package. One exemplary configuration is known that a block is formed on a stem of the CAN type package, and the laser diode is mounted on the block via a substrate made of aluminum nitride (AIN), which operates as a heat sink. In addition to the laser diode disposed on the heat sink, a thin film metal resistor is also formed on the AIN substrate, and electrical connection from the resistor to the lead of the package and the semiconductor are carried out by micro-strip lines.
According to such configuration of the optical transmitting module with the CAN type package, since the termination resistor can be provided within the package as a thin film resistor, the module may operate and emit light in GHz band with quality.
However, in such optical transmitting module, an insulating material having good thermal conductivity must be prepared to form the thin film resistor and to mount the laser diode thereon. Such materials are so restricted, in the present circumstances, only the aluminum nitride is known, but is so costly. Moreover, to use the thin film configuration must be taken the parasitic capacitance attributed to the device into consideration.
Therefore, one object of the present invention is to provide a arrangement of the optical transmitting module that installs the laser diode and the termination resistor therein, and shows a superior high frequency performance without using any particular materials or configurations.